The Exploration and Exploitation of an SD Memory Card

by xobs & bunnie

All “managed FLASH” devices, such as SD, microSD, and SSD, contain an embedded controller to assist with the complex tasks necessary to create an abstraction of reliable, contiguous storage out of FLASH silicon that is fundamentally unreliable and unpredictably fragmented. This controller is an attack surface of interest. First, the ability to modify the block allocation and erasure algorithms introduces the opportunity to perform various MITM attacks in a virtually undetectable fashion. Second, the controller itself is typically powerful, with performance around 50MIPS, yet with a cost of mere pennies, making it an interesting and possibly useful development target for other non-storage related purposes. Finally, understanding the inner workings of the controller enables opportunities for data recovery in cards that are thought to have been erased, or have been partially damaged.

This talk demonstrates a method for reverse engineering and loading code into the microcontroller within a SD memory card.